Conceptual design of a small long life fast reactor core loaded with Pu without extracting MAs

A design study of a small long life sodium cooled fast reactor core with ternary alloy U-Pu-Zr as fuel has been completed in the paper, the purpose of which is, under the strategy of non-separation of MAs from Pu, to investigate general effects on core characteristics of adding MAs into the core or blanket region and to demonstrate the feasibility of loading Pu without extracting MAs as drive fuel in the design. Calculation results indicate that: when MAs is added into core with hard neutron spectrum the burnup reactivity swing can be reduced effectively and considerable qualities of MAs can be incinerated. Concurrently, main disadvantage in such cases is the decreasing of βeff, Λ and Doppler feedback, but not markedly if the amount of MAs added is small. Na void worth, which increases rapidly with the addition of MAs, is always the severest problem; when MAs is added into blanket, the initial Keff will be reduced, burnup reactivity swing will be larger and transmutation rate of MAs will be lower as the spectrum in this region is softer than in core region. However, on the other hand, MAs addition into blanket brings fewer penalties of kinetic parameters (βeff and Λ) and reactivity feedback (Doppler coefficient and Na void worth) compared to MAs addition into core. Finally, Pu from Daya Bay reactor spent fuel without extracting MAs is considered as drive fuel loaded into core. The results show that, as the MAs percentage in TRU is small, impacts on core performance are insignificant (basically, variations of βeff, Λ and Doppler coefficient less than 10%) except Na void worth and, at the same time, benefits of high fuel proliferation resistance and considerable amount of burned MAs can be obtained simultaneously. (author)